investigating TGP / GBU-31 issue: unable to lock top of bunker and significant misses in hilly terrain

[dutchili]

Tacview-20240425-164316-DCS-bomb tet.zip.acmibomb tet.mizGBU31 misses.trk

 

Expected behavior: TMS up leads to point track where i point. Bomb drops on point track target

Actual behavior: TMS up leads to the TGP moving, Bomb drops short of target.

[dutchili]

@NineLine

[dutchili]

@BIGNEWYstill waiting for a response and fix

[Lord Vader]

Hi @dutchili

The supplied track includes mods. Please try to recreate your issue in a clean mission for our analysis, preferably in Caucasus for simplification.

Regarding the way you describe your issue, however, seems to indicate you're trying to designate the top of an object. It is advised to always designate the very bottom of the object. This is an optical "lock" performed by the TPOD, prone to be affected by parallax errors that can create an illusion the SPI is moving.

In any case, we need to see what you are trying to do to be sure this is the case. 

[dutchili]

There you go @Lord VaderGBU38 misses.trk
GBU38 this time, but same issue. Laser seems to point through the object and bridge towards the solid ground.

[Lord Vader]

@dutchili

Again, please read what I wrote above.

On 8/16/2024 at 10:23 AM, Lord Vader said:

It is advised to always designate the very bottom of the object. This is an optical "lock" performed by the TPOD, prone to be affected by parallax errors that can create an illusion the SPI is moving.

The object you are trying to hit is set on a bridge. The only way to correctly hit it in that condition is to aim at the bottom of that bridge. Remember we're operating coordinates, not visual locks. I took control of your track, aimed the TPOD at the bottom of the bridge, TMS up, dropped the JDAM and it hit the target.

[razo+r]

11 minutes ago, Lord Vader said:

@dutchili

Again, please read what I wrote above.

The object you are trying to hit is set on a bridge. The only way to correctly hit it in that condition is to aim at the bottom of that bridge. Remember we're operating coordinates, not visual locks. I took control of your track, aimed the TPOD at the bottom of the bridge, TMS up, dropped the JDAM and it hit the target.

What about putting the TGP on the bridge and fire the laser? Shouldn't that update the coordinates to the bridge in the air? 

[jackdaw]

@dutchiliI believe DCS works out where the ground cordinates are and that is where the bomb - misile hits, whether that is how it works IRL may be different

[dutchili]

52 minutes ago, Lord Vader said:

@dutchili

Again, please read what I wrote above.

The object you are trying to hit is set on a bridge. The only way to correctly hit it in that condition is to aim at the bottom of that bridge. Remember we're operating coordinates, not visual locks. I took control of your track, aimed the TPOD at the bottom of the bridge, TMS up, dropped the JDAM and it hit the target.

Isn't the TGP supposed to simulate a coordinate (X,Y and Z) resulting from the reflected laser beam?
If have multiple occurrences of bombs missing, with and without mods, where the visual point the TGP is pointing at is not where the bomb is going. Sometimes the TGP is even moving after TMS up. Especially in mountainous terrain.
I would say this is a bug rather than a feature.

[BIGNEWY]

2 hours ago, dutchili said:

Isn't the TGP supposed to simulate a coordinate (X,Y and Z) resulting from the reflected laser beam?
If have multiple occurrences of bombs missing, with and without mods, where the visual point the TGP is pointing at is not where the bomb is going. Sometimes the TGP is even moving after TMS up. Especially in mountainous terrain.
I would say this is a bug rather than a feature.

Hi, 

the problem is sometimes the model of the various structures in DCS can create issues, its often best to have your aim point at the base of the structure, this will ensure a higher hit rate generally. 

thank you 

[dutchili]

I wonder if this classifies as a bug and should be reported to the developers.

[BIGNEWY]

It is known, and I will mention it to the team again. 

thank you 

[dutchili]

thank you

[Hobel]

vor 5 Stunden schrieb razo+r:

What about putting the TGP on the bridge and fire the laser? Shouldn't that update the coordinates to the bridge in the air? 

This is possible and works very well, it also works with buildings but here the ground is hit.
With the bunker mentioned here, you hit also roof with this method

 

 

  

Am 16.8.2024 um 13:52 schrieb dutchili:

There you go @Lord VaderGBU38 misses.trk
GBU38 this time, but same issue. Laser seems to point through the object and bridge towards the solid ground.

I looked at the track and the mistake here is, you stop lasing and then you throw the bomb, the bomb misses.
I would expect the last position of the laser to be saved and not immediately thrown overboard as soon as you stop lasing.

test it again just hold the laser down when dropping

here you can see that the laser coordinates are discarded after a few seconds:

 

 

 

 

Edited August 19, 2024 by Hobel

[dutchili]

Interesting. I would expect he coordinate to not change

[dutchili]

This issue still excists, bump! @BIGNEWY

 

It is hard to hit a bridge. The object height seems not be added to the ground altitude.

In this example mission, the ME lists the altitude equal for the water and the bridge (which cannot be right). Also, the elevation of the water as displayed by the ME differs significantly on different area's of the lake, suggesting that the water depths are also ignored.

During the miz, the TGP points at the water below the bridge.

When lasingBridge strike test.miz the road on the bridge, the elevation is different from what the ME reads and the actual elevation of the road. Out of 5 tests, at least one bomb misses the road by underflying or overflying the target. For GPS bombs, waypoints create in the ME or on the fly are far from exact.

[BaronVonVaderham]

Still an issue. Any ETA fire a fix?

[KengBeng]

Bump! When will this be fixed?

[Hobel]

vor 3 Stunden schrieb dutchili:

This issue still excists, bump! @BIGNEWY

 

It is hard to hit a bridge. The object height seems not be added to the ground altitude.

In this example mission, the ME lists the altitude equal for the water and the bridge (which cannot be right). Also, the elevation of the water as displayed by the ME differs significantly on different area's of the lake, suggesting that the water depths are also ignored.

During the miz, the TGP points at the water below the bridge.

When lasingBridge strike test.miz the road on the bridge, the elevation is different from what the ME reads and the actual elevation of the road. Out of 5 tests, at least one bomb misses the road by underflying or overflying the target. For GPS bombs, waypoints create in the ME or on the fly are far from exact.

So the problem is that the ME is not able to include height differences of buildings or bridges?

[dutchili]

14 minutes ago, Hobel said:

So the problem is that the ME is not able to include height differences of buildings or bridges?

Yes, and: waypoints created while flying (mark / TGP lase) have the wrong elevation too.